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The development of atrial fibrillation was associated with a more rapid decline in cognitive function among older adults, even in the absence of clinical stroke, researchers found.

At age 75 and older, scores on the Modified Mini-Mental State Examination (3MSE) declined by about 3 points more for every 5 years of aging for individuals who developed atrial fibrillation compared with those who did not develop the arrhythmia, according to Evan Thacker, PhD, of the University of Alabama at Birmingham, and colleagues.

The findings were similar for scores on another test of cognitive function, the Digit Symbol Substitution Test, with declines that were about 2 points greater for every 5 years of aging among those who developed atrial fibrillation, the researchers reported online in Neurology.

"The more rapid decline we observed after incident atrial fibrillation suggests that people with atrial fibrillation are likely to reach thresholds of cognitive impairment or dementia at earlier ages than people with no history of atrial fibrillation," Thacker and colleagues wrote.

In the current study, in fact, the age at which the average predicted 3MSE score dropped below 78 -- shown to be an accurate cutoff for detecting dementia -- was 2 years younger among those who developed atrial fibrillation (85 versus 87).

Previous studies have revealed associations between atrial fibrillation and cognitive decline and dementia -- including a meta-analysis and a post-hoc analysis of two randomized trials -- in patients with and without clinical stroke. But there is not as much information about changes in cognitive test scores over time.

Thacker and colleagues explored the issue using data from the Cardiovascular Health Study, a community-based study of individuals 65 and older. None of the participants had atrial fibrillation or a history of stroke at baseline. During follow-up, patients were censored when they had a stroke.

The current analysis included 5,150 men and women with a mean age of 73 at baseline. Through an average follow-up of 7 years, 10.7% developed atrial fibrillation.

After adjustment for several baseline characteristics, the individuals who developed atrial fibrillation had accelerated declines in cognitive function compared with those who did not develop the arrhythmia.

The predicted decline in 3MSE scores over the next 5 years of aging for someone who was 80 years old, for example, was 6.4 points among those who did not have a history of atrial fibrillation and who remained free from the arrhythmia and 10.3 points among those who developed atrial fibrillation.

Similar relationships were seen when atrial fibrillation occurred at ages 75 and 85, but not at age 70.

Thacker and colleagues proposed embolic infarction as a possible explanation for the associations. Even though patients with clinical stroke were excluded, it is possible that some strokes went undetected.

"Embolic infarcts may be covert and fail to cause noticeable symptoms but produce lasting tissue damage and functional consequences, which could be a potential explanation for the results we observed," they wrote.

Another possible mechanism underlying the relationships could be cerebral hypoperfusion, they wrote, adding, however, that it is possible that atrial fibrillation is a marker of other factors that impair cognition or that cognitive decline increases the risk of atrial fibrillation.

The authors acknowledged that the study could be limited by an incomplete assessment of atrial fibrillation if it did not result in symptoms or the patients did not seek care for symptoms. In addition, there was no information on the type of atrial fibrillation and some cognitive scores were missing.

This research was supported by the National Heart, Lung, and Blood Institute (NHLBI), with additional contribution from the National Institute of Neurological Disorders and Stroke (NINDS). Additional support was provided by the National Institute on Aging (NIA). Thacker was supported by an NHLBI training grant. His co-authors reported support from the NIA and NHLBI.

Thacker reported that he had no conflicts of interest. His co-authors reported relationships with Medtronic and Merck/American Geriatrics Society.

Todd Neale, MedPage Today Staff Writer, got his start in journalism at Audubon Magazine and made a stop in directory publishing before landing at MedPage Today. He received a B.S. in biology from the University of Massachusetts Amherst and an M.A. in journalism from the Science, Health, and Environmental Reporting program at New York University.

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